Phase‐Coherent Amplification of Ocean Swells Over Submarine Canyons
Phase‐Coherent Amplification of Ocean Swells Over Submarine Canyons
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DOI：
10.1029/2019jc015301
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发表时间：
2020-02
影响因子：
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通讯作者：
H. Tamura;K. Kawaguchi;Takashi Fujiki
中科院分区：
文献类型：
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作者：
H. Tamura;K. Kawaguchi;Takashi Fujiki
海洋涌浪可能是一个重大的沿海灾害，可能造成沿海灾害，对基础设施造成昂贵的破坏，并造成悲惨的生命损失。我们在日本海富山湾的沿海地区观察到了这一点，该地区受到严重的冬季涌浪事件（所谓的YoriMawari‐nami; YM波）的破坏。2008年2月记录了一次极端涌浪事件，海湾一个地点的波高达到9米以上，相当于当地气候平均值的16倍。日本海岸工程界已经花费了大量的努力来用相位平均波模型再现YM波事件，但据我们所知，没有成功。在原型YM事件期间，我们发现诺托半岛过滤了入射波场，使得海湾中的入射波是准单色的。涌浪然后在海底峡谷上折射，导致波能的双峰方向分布。这引发了有利于相干干扰的条件，违反了相位平均方法的假设。相干干涉是理解大振幅形成和匹配观测到的高时空变异性的关键机制。我们的研究结果证明了相干干涉对海岸测深波浪统计的重要性;只有通过考虑相位分辨现象，我们才能够充分再现观测结果。
Ocean swells can be a significant coastal hazard, potentially causing coastal disasters with costly damage to infrastructure and tragic loss of lives. We have observed this in the coastal region of Toyama Bay in the Sea of Japan, which has been devastated by severe winter swell events (the so‐called YoriMawari‐nami; YM wave). An extreme swell event was recorded in February 2008 in which the wave height at a site in the bay reached 9+ m, which corresponds to 16 times the local climatological average. Substantial efforts by the Japanese coastal engineering community have been expended to reproduce YM wave events with phase‐averaged wave models but, to our knowledge, with no success. During an archetype YM event, we found that the Noto peninsula filtered the incoming wavefield such that in the bay incident waves were quasi‐monochromatic. The swell then refracted over a submarine canyon resulting in a bimodal directional distribution of wave energy. This initiated conditions favorable for coherent interference, violating the assumptions of the phase‐averaged approach. Coherent interference is the key mechanism for understanding the formation of the large amplitudes and for matching observed high space‐time variability. Our results demonstrate the significance of the coherent interference for wave statistics over coastal bathymetry; only by accounting for phase‐resolving phenomena were we able to adequately reproduce the observations.